Add WebUSB bindings and client interface [part 1]

Source/modules/webusb/NavigatorUSB.idl

Index: Source/modules/webusb/NavigatorUSB.idl
diff --git a/Source/modules/webusb/NavigatorUSB.idl b/Source/modules/webusb/NavigatorUSB.idl
new file mode 100644
index 0000000000000000000000000000000000000000..e1bdb68241f49fdf04208084639627ae6f823d4d
--- /dev/null
+++ b/Source/modules/webusb/NavigatorUSB.idl
@@ -0,0 +1,12 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// http://reillyeon.github.io/webusb/#device-enumeration
+
+[
+    GarbageCollected,
+    RuntimeEnabled=WebUSB,
+] partial interface Navigator {
+    readonly attribute USB usb;
+};